This invention relates to a binocular reflecting telescope which is a variant of a Cassegrain or Schmidt-Cassegrain reflector and an equatorial mount for supporting the same.
As a conventional astronomical binocular, there is known a right-angle view refracting binocular as shown in FIGS. 22, 23. It uses a roof (Amici) prism 102 and a parallelogrammic prism 103. The light beam from an objective lens 101 is reflected by the roof (Amici) prism 102 at points P1 and P2 and guided to an eyepiece 104 through a parallelogrammic prism 103.
Another type of conventional binocular is shown in FIG. 24, which is a Cassegrain reflector. This reflecting telescope comprise a Cassegrain telescope tube housing primary mirrors 110, 110' having small holes 111, 111' and secondary mirrors 112, 112' and Porro prisms 113, 113' combined with the telescope tube. The light reflected by the primary mirrors 110, 110' is reflected again by the secondary mirrors 112, 112' for condensing, passed thorough the small holes 111, 111' reflected by the Porro prisms 113, 113' and guided to eyepieces 114, 114'.
Such binoculars have to be supported on a rather large equatorial mount if they are large-apertured ("large" usually means more than 500 mm). An equatorial mount generally has a telescope tube rotating device mounted on one end of a declination shaft so as to be rotatable about a polar axis to rotatably support such a binocular.
But, with the binoculars using a roof (Amici) prism or a Porro prism, the back focus behind the primary mirror has to be considerably long corresponding to the length of the prism light path. Thus, they tend to be long in the focal length and narrow in the visual field.
Another problem is that the eye-pieces are rotated as the telescope is turned. This means that when mounted on an equatorial mount, as the telescope is turned following the diurnal motion of a heavenly body, an observer is forced to incline his head and take an unnatural body position.
Further, a conventional equatorial mount having a telescope tube rotating device tends to be large in size and heavy, so that it is difficult to operate, and is also expensive.
An object of this invention is to provide a binocular reflecting telescope which may be applied to small-apertured or large-apertured telescopes, which has a short focus and thus a short primary telescope tube even if it has a large aperture, which has a bright and wide visual field and is compact in size and inexpensive and which has rotatable eye-pieces so that an observer does not have to incline his head while observing.
Another object is to provide an equatorial mount, for supporting the above-described telescope, which has a greater degree of freedom of rotation than a conventional German style equatorial mount and which is sufficiently light in the total weight including the counterweights for keeping the weight balanced and thus is inexpensive and easy to operate.